The present invention generally relates to carbon nanotubes (CNTs), and more specifically to CNTs incorporated in composite materials.
Carbon nanotubes (CNTs”) exhibit roughly eighty times the strength, six times the toughness, as indicated by Young's Modulus, and one-sixth the density of high carbon steel. Due to these favorable mechanical properties, CNTs have been used as a reinforcing element in composite materials. CNT-based composites can be less dense than many metals, while providing improved strength and corrosion protection. CNTs also exhibit favorable properties for thermal and electrical applications as well.
Most processes for producing CNT-based composites involve direct mixing of loose CNTs or bundled CNT-based yarns into the matrix material of the nascent composite. When employing CNTs in this manner in a typical resin-type matrix material, the resultant composites are typically limited to a maximum of about three weight percent of carbon nanotubes in the finished composite material. The reason for this limitation is the resulting increased viscosity of the matrix and a decreased ability to impregnate the resulting composite.
CNTs have also been employed in hybrid composites in which two, three, or more different reinforcing elements are incorporated within a composite. Hybrid composite systems which incorporate nanoscale reinforcements require additional processing steps to properly disperse the nanoparticles, including CNTs. CNT incorporation into a matrix has the added challenge of controlling CNT orientation which adds to the processing complexity. Moreover, limitations on CNT loading due to various factors, such as large viscosity increases have been observed in hybrid composite systems as well.
Hybrid composite manufacturing processes become increasingly complex if variable CNT loading or different CNT types are needed in different portions of a composite structure. It would be beneficial to decrease the complexity of manufacture of CNT composites and tailored hybrid composites and to provide composite articles with improved CNT loading capacity while also controlling CNT orientation. The present invention satisfies these needs and provides related advantages as well.